Cadaverine is a platform chemical involved in the production of various products. Bio-based production of cadaverine has gained research interest since the 1980s. Cadaverine can be synthesized via decarboxylation of lysine in microorganisms. Currently, biosynthesis of cadaverine is performed using two strategies: fermentative production or in vitro enzyme catalysis.
In a fermentative production of L-lysine approach, a lysine decarboxylase gene is added to a lysine producing bacteria strain (e.g. Corynebacterium glutamicum and Escherichia coli (E. coli)) to extend the lysine biosynthesis pathway to a cadaverine biosynthesis pathway. However, the reported cadaverine yield is lower than the lysine yield for other Corynebacterium glutamicum strains lacking the lysine decarboxylase gene. Such low yield may be due to the toxicity of the cadaverine product to the producing bacterial strain.
Alternatively, bacteria can be engineered or induced to produce lysine decarboxylase for the in vitro enzyme catalysis. One strategy involves inducing expression of a chromosomally encoded lysine decarboxylase gene in an un-engineered Hafnia alvei (H. alvei) strain. However, the reported yield of the enzyme is low. Another strategy involves engineering recombinant strains. For example, Japanese companies (JP2009028045, U.S. Pat. No. 7,189,543, CN102056889) have reported the construction of E. coli recombinant strains that over-express lysine decarboxylase and utilize either whole cell or cell lysate for catalysis. However, expression of large amounts of polypeptides that are toxic to the host cell causes expression plasmid instability over serial passage. Antibiotics are required in the medium to ensure plasmid stability during the culture.
Use of antibiotics may cause development of antibiotic resistant bacteria, and maintains high levels of antibiotic resistant microorganisms in the environment. See, e.g. Martinez, “Environmental pollution by antibiotics and by antibiotic resistance determinants,” Environmental Pollution (2009), Vol. 157, Issue 11, 2893-2902. However, antibiotic resistant bacteria potentially pose health and/or environmental hazards. Thus, there remains a need for a more effective recombinant plasmid vector that can remain stable through multiple rounds of serial passage without antibiotic selection.